The synthesis and structure of sterically encumbered terphenyl tin(II) halide derivatives: simultaneous existence of monomers and dimers in the crystalline phase

Abstract The reaction of Et 2 O·LiC 6 H 3 -2,6–Trip 2 (Trip=C 6 H 2 –2,4,6- i -Pr 3 ) with SnCl 2 afforded the two coordinate monomer Sn(Cl)C 6 H 3 -2,6–Trip 2 ( 1 ), and its dimer {Sn(μ-Cl)C 6 H 3 –2,6-Trip 2 } 2 ( 2 ), as orange and yellow crystals, respectively. Solution 119 Sn NMR spectroscopy of 2 in C 6 D 6 solution showed that it dissociated readily to give 1 . The addition of pyridine (py) to a solution of 1 yielded the adduct py·Sn(Cl)C 6 H 3 –2,6-Trip 2 ( 3 ) which featured tin in a three coordinate pyramidal environment. The reaction of the closely related bulky terphenyl lithium reagent LiC 6 H 3 –2,6-Dipp 2 (Dipp=C 6 H 3 –2,6- i -Pr 2 ) with SnCl 2 afforded the mixed halide species {Sn(μ-Cl) 0.35 (μ-I) 0.65 C 6 H 3 –2,6-Dipp 2 } 2 ( 4 ). This arose from the preparation of the lithium aryl precursor in situ from IC 6 H 3 –2,6-Dipp 2 and n -BuLi. The monomeric nature of 1 , and the weak association of 2 and 4 , were attributed to the large size of the terphenyl ligands. All compounds were characterized by X-ray crystallography, 1 H, 13 C and 119 Sn NMR spectroscopy, and IR and UV–Vis spectroscopy.